Amplified Detection of\nDNA through the Enzyme-Free\nAutonomous Assembly of Hemin/G-Quadruplex DNAzyme Nanowires

Abstract

An enzyme-free amplified detection platform is described\nusing\nthe horseradish peroxidase (HRP)-mimicking DNAzyme as an amplifying\nlabel. Two hairpin structures that include three-fourths and one-fourth\nof the HRP-mimicking DNAzyme in caged, inactive configurations are\nused as functional elements for the amplified detection of the target\nDNA. In the presence of the analyte DNA, one of the hairpins is opened,\nand this triggers the autonomous cross-opening of the two hairpins\nusing the strand displacement principle. This leads to the formation\nof nanowires consisting of the HRP-mimicking DNAzyme. The resulting\nDNA nanowires act as catalytic labels for the colorimetric or chemiluminescent\nreadout of the sensing processes (the term “enzyme-free”\nrefers to a protein-free catalyst). The analytical platform allows\nthe sensing of the analyte DNA with a detection limit corresponding\nto 1 × 10^–13 M. The optimized system acts as\na versatile sensing platform, and by coaddition of a “helper”\nhairpin structure any DNA sequence may be analyzed by the system.\nThis is exemplified with the detection of the BRCA1 oncogene with\na detection limit of 1 × 10^–13 M.